Interrupter part of compressed-air breakers



Jan. 27, 1953 B. P. BAKER Erm. 2,627,005

INTERRUPTER PART OF COMPRESSED-AIR BREAKERS Filed Feb. 5, 1949 2SHEETS-SHEET 1 24 20 2| T l 2Is i 12s j i |2M n 12- n s E 11i--` `|2B|70/` |7sA r` AIB lo zl." 3| /'ll |85 Ils le 30 ,29 A s 2 :zIS 28 24 Flg, I.

WlTNEssEs; INVENTORS l Benjamin .R Boker, Erhng Frisch, WMM a John B.MocNeiu.

Wo ne S. As e y DB @www

ATTORNEY Jan. 27, 1953 B.- P. BAKER Erm. 2,627,005

INTERRUPTER PART oF ooMRREssEn-AIR BREAKERS Filed Feb. 5, 1949 2SHEETS-SHEET 2 WITNESSES: g INVENTORS Benjamin P. Boker, Erling Frisch,Wayne S. AspeYBx John B. MocNell.

ATTORNEY Patented jan. j27, 1953 UNITED STATES PATENT OFFICE INTERRUPTERPART OF COMPR-ESSED-AIR BREAKERS Application February 3, 1949, SerialNo. 74,406

16 Claims. (Cl. 200-148) Our invention relates to compressed-aircircircuit-breakers, and it has particular relation to the interrupterpart of a self-opening, singlecolumn, longitudinal-blast circuit-breakerhaving two contacts in series.

Heretofore, various types of compressed-air circuit-breakers have givenan excellent account of themselves, both in this country and abroad, byreason of considerations of their safety, continuity of service, andreduced maintenance. These breakers, in the past, have been very greatlyhandicapped, however, by reason of their relatively high cost, and aconsiderable complexity of construction.

Our invention is the culmination of a designdevelopment in which we haveproduced an extremely simple, practical, and inexpensive form ofinterrupter-assembly, which constitutes a specic detail or improvementof the subject matter of a copending application, of Benjamin P. Bakerand Howard M. Wilcox, Serial No. 73,515, iiled January 29, '1949, andnow abandoned, which covers the general assembly of a compressed-airbreaker which is mounted with an insulating blast-tube extending up fromthe top of a compressed-air reservoir, and having an extension of theblast-tube extending down inside of the tank and terminating in ablast-valve disposed at the bottom of the tank, and having asinglecolumn multi-gap air-blast arrester-assembly mounted at the top ofthe insulating tube,

Our present invention relates to a practical form of theinterrupter-assembly, for this combination, in which a novel, removable,doubleended, moving-contact assembly carries not only the moving arcingcontacts, but also the cluster of segmental contact-fingers whichconstitute the main contacts. Our invention relates to an assembly inwhich these main and arcing contacts can be compressed or retractedtoward each other, and in that state moved laterally out of a box-likeholder, thereby exposing the tips of the two stationary contacts betweenwhich the double-ended moving-contact assembly is normally inserted.This makes it possible to service both the stationary contacts and themoving contacts. The use of the cluster of main contactsegments7 inaddition to the arcing contacts, makes possible the design of ourassembly for a full-load line-current in excess of 2000 amperes.

Another object of our invention is to provide a special design ofbreaker, with two gaps, or sets of contacts, in series with each other,one gap being shunted by a shuntng impedance, and the other gap beingdesigned so that there is a CII delay in the time at which this secondgap receives a sufficient compressed-air pressure for separating thegap-contacts, so that the faultcurrent is rst partially interrupted bythe firstacting gap, and thereby transferred to the shunting impedance,which very considerably reduces the magnitude of the current which hasto be nally interrupted by the second-operating gap. The two gaps arepreferably differently designed, so as to advantageously handle thedifferent circuit-interrupting duties which are imposed thereon, as willbe subsequently described. By this means, we are enabled to interruptcurrents up to 37,000 amperes at 44,000 volts, corresponding to 4.9million-kilovolt amperes on a 3-polc, 69-kilovolt breaker, with a totalcircuit-interrupting time, from the rst energizing of the trip-coil tothe iinal interruption of the current iiowing through the shuntngimpedance, ranging from 2.3 to 3.3 cycles, on a -cycle line.

A further object of our invention is to provide a novel double-gapinterrupter-assembly of the class described, having two exhaust-chamberswhich materially contribute to the success of the functional operationof the device, as will be subsequently explained.

A more specific object of our invention is to provide a novel structureof the hollow longitudinal-blast stationary-electrode, having a specialperforated arc-terminal device supported centrally therein at a pointspaced slightly back from the orice in the tip of said stationaryelectrode.

With the foregoing and other objects in view, our invention consists inthe combinations, assemblies, systems, structures, parts, and methods ofdesign and operation, hereinafter described and claimed, and illustratedin the accompanying drawing, wherein Figure l is a side elevationalview, partly in section, and largely diagrammatic, not to scale,indicating the general principles of our invention as applied to asingle-pole assembly, Fig. 2 is a side elevational View of themoving-contact assembly, removed from the circuit-breaker, and Fig. 3 isa longitudinal sectional view of the interrupter-assembly, showing theimpedance-shunted contacts in their open, arcing condition, while theother contacts are still closed, with a diagrammatic indication of theshuntng impedance.

Figure 1 shows a single pole of a compressedai-r breaker-assemblyembodying our invention. It is to be understood, however, that ourinvention is often or usually applied to a three-phase power-system, inwhich case each pole would consist of the structure as shown in Fig. l,except that a single operating-mechanism may be used for gang-operationof all three poles, and possibly also a single compressed-air tank mightbe used for supporting the blast-tubes of all three poles.

Each pole of the breaker preferably has its own compressed-air tank orreservoir I, which is made of steel, and which serves also as asupporting-structure for the rest of the assembly. We provide avertically disposed, insulating, blast-tube 2 which extends upwardlyVabove the top of the tank and is supported by the tank. Inside of thetank, there is a vertically disposed tube-means 3, which is inalignment, and airflow communication, with the bottom of the blast-tube2, so that said internal tube-means 3 serves, in effect, as a blast-tubevextension which extends downwardly, within the tank, to a point near,but spaced from, the bottom of the tank, as indicated, at 4. Physically,this blasttube extension, inside of the tank, could be a pari; of theinsulating blast-tube 2 which couldv be made long enough to extend downtothe point il near the bottom of the tank, but actually, it is moreconvenient to make the internal tubemeans 3 out of iron or steel whichis weldedk or otherwise properly secured within the tank I. Also, in apractical construction, it Would be possible for the internal tube-means3 te comprise the top part of an internal tube which physically extendsfrom the top of the tank all the way down to the bottomV of the tank,but which is provided with side-openings at the effective tube-bottom t,so that said tube-means would be inta-ct, as a tube, only above thepoint Disposed within the tank I, under the bottom 4 of the tube-means3, is a blast-valve 5, which is accessible and operable from the bottomof the tank. The blast-valve 5 is preferably a differential-pressurevalve, having a vertically movable inverted-cup member 6, which ispressed up, by a compression-spring '1, into tight seating-engagementwith the bottom end 4 of Vthe tubemeans 3, as claimed in theaforementioned Baker- Wilcox application. The compression-spring I actsVas a weak closing-spring, which does not exert enough, pressure to closethe valve against the air-pressure in the tank I, which may be atsomething of the order of 250` pounds per square inch. Normally, theblast-valve 5v is held closed by being supplied, from underneath, withair at the same pressure as the air in the tank I, as by means of avalve-controlling pipe 8, which is in communication with the undersideof the movable inverted cup 6, so that the valve is thus held closed.The valve is opened by releasing the air-pressure which is applied bythe valvecontrolling pipe 8, thus permitting the air-pressure within thetank to push down the inverted cup 6, thus permitting air to rush, inlarge quantities, upwardly through the internal tube-means 3 and throughthe insulating blast-tube 2.

On top of the insulating blast-tube 2, we mount a single-columninterrupter-assembly IIJ, which is preferably supported in a verticalposition, in alignment with the blast-tube 2, and which is physicallysupported solely, or substantially entirely, by the blast-tube, so as tobe electrically insulated from ground by said blast-tube. Thissingle-column interrupter-assembly comprises a plurality of verticallyaligned, self-opening, longitudinal-blast interrupter-gap devices II andI2, two such gap-devices being used on a 69kilovolt breaker asillustrated. These galli-d,evicesA I I and I2 are electrically connectedin series, so that the current-flow, in the normal closed position ofthe breaker, is yfrom the top I3 of the interrupterassembly I to thebottom Iii thereof, a suitable line-terminal I5 being provided at thetop I3. Each interrupter-gap device II and I2 comprises a stationarycontact-member IIS or I2S, as the case may be, and a vertically movablecontactmember IIM or IEM, as the case may be. The two movablecontact-members I IM and I2M are normally biased toward closed positionby means of biasing-springs IIB and I2B respectively.

In the construction which is very much preferred, the iirst stationarycontact-member IIS is at the bottom Id of the interrupter-assembly IIJ,and is integrally or electrically united with a lower exhaust-chamber I,which is made of metal. The stationary contact-member IIS is hollow, andextends down into the lower exhaustchamber I, as shown at I6.

In the preferred construction, the two movable contact-members II M andI2M are mounted within a metallic moving-contact assembly or housing I'I which is in the form of two c-oncentric cylinders, namely an innercylinder Iii and an outer cylinder I'Io, so as te provide an annularspace or an enclosed interrupting chamber Ils between these cylinders,through which the airblast may pass.

The moving-contact housing I l is vertically spaced from the lowerexhaust-chamber I6 by means of an insulating tube I8, which Supports theouter cylinder Io, and which is larger than the lower stationarycontact-member IIS, so as to provide an annular space I 8s therearound,through which the air-blast may pass. In order to guide the air-blastfrom the blast-tube 2 into the annular space ISS, the lowerexhaust-chamber I6 is provided with a funnel-like air-guiding duct IS,which is spaced from the lower end IS," of the lower stationarycontact-member IIS, so as to provide an annular space Its through whichthe air-blast may pass, in moving upwardly from the blast-tube 2 intorthe annular space I8s.

The upper stationary contact-member I2S is integrally or electricallyunited with an upper exhaust-chamber 20, which is similar to the lowerexhaust-chamber I6, except that it lacks the funnel or duct I9 forcarrying the blast-air upwardly on through the upper exhaust-chamber 20.The upper stationary contact-member IZS is likewise of hollowconstruction, and its upper end is in communication with the spacewithin the upper exhaust-chamber 2 0'. "This upper exhaust-chamber 20 issupported on the top end of an insulating tube 2|, which is similar tothe tube I8, except that the lower end of the top insulating tube 2lrests on top off the outer cyl'- inder I'Io of the moving-contacthousing I1. This upper insulating tube 2| is also larger than the upperstationary contact-member IZS, so as to provide an annular space 2Iswhich forms a closed upper end for the blast-air, as this blastinitially moves upwardly through the interrupterassembly IIJ.

In the construction which is very much preferred, as illustrated, theupper end of the lower stationary contact-member IIS, and the lower endof the upper stationary contact-member I2SV are each provided with acentrally disposed orice 22, which is normally closed by the cooperatingmovable contact-member IIM or I2M, as the case may be. The configurationof these movable contact-members IIM and IEM is such that the pressureof the blast-air operates on these movable contact-members IIM and |2Mto press them back away from their respective stationary contact-membersIIS and I2S, thus making the gap-devices II and I2 self-opening, thatis, making them open automatically, by themselves, as soon as asuilicient gas-pressure is built up in the spaces around them, withoutrequiring any other device, not a part of the moving-contact assemblyIl, for causing a separating-movement of the movable contact-members HMor I2M. This opening-movement of the movable contact-members HM and I2Mdraws arcs between said members and their associated stationarycontact-members IIS and I2S, respectively, thus initiating acircuit-interrupting operation of the breaker.

As soon as each movable contact-member IIM or I2M moves away from itsnormal contact-making engagement with the end of its associatedstationary contact-member IIS or I2S, as the case may be, it uncoversthe 'orifice 22 in the hollow stationary contact-member IIS or I2S, thuspermitting a blast of air to move longitudinally, or in a verticaldirection, through the orice 22 and thence through the hollow stationarycontactmember HS or I2S, and thus acting powerfully to extinguish thearc between the movable and stationary contact-members. The upper end ofthe hollow upper stationary contact-member I2S dumps its air directlyinto the upper exhaust-chamber 20, and the lower end of the lower hollowstationary contact-member I IS exhausts its blast of air into the lowerexhaustchamber I6 by means of a plurality or" tubular openings 23, whichpass through the lower end I6' of the hollow lower stationarycontact-member IIS, and also through the funnel or duct I9 in the lower`exhaust-chamber I6.

These upper and lower exhaust-chambers 20 and IB thus provide anexpansion-space in which i* the longitudinally moving air-blasts withinthe two stationary contact-members IIS and I2S may accumulate during thebrief time which is required for a complete circuit-interruption. It maytake the blast something like 1A; cycle, (assuming a 60-cycle line),before the arcing-contacts Ibegin to separate, and then a time somethinglike cycle for the maximum contactseparation to be achieved. Then thearc may hang on for an additional time which may be slightly longer thanthe longest current-flow period or half-cycle which could be expectedunder asymmetric-wave conditions. It is desirable for the arc to beinterrupted at or before the rst important current-zero, (or sometimespossibly the second one), after full contact-separation has beenachieved, disregarding, (as unimportant from an arc-interruptingstandpoint), any current-zero which may occur very soon after fullcontact-separation is obtained. Then it is desirable to prevent arestriking of the arc on the next half-cycle, and to this end it isnecessary to have a large quantity of air-movement, a high air-velocity,high turbulence, and cooling, or a combination of these factors. Andthen, in subsequent half-cycles, it is desirable to continue to have asucient dielectric strength of the air in the arcing-gap, so as toprevent any subsequent arc-restriking, and for this purpose, theairpressure of the once-deionized and cooled gapair is of service inproviding dielectric strength to prevent a later breakdown of the gap.

Our upper and lower exhaust-chambers 20 and I6 provide the gas-pressurein the gap-space. The initial blast must be maintained until at leastthe first (or second) important currentzeroafter full gap-separation hasbeen reached, but when the back-pressure in these exhaustchambersreaches as much as something like 50% of the pressure at thehigh-pressure side of the orifice or arcing-gap, the blast no longertravels at approximately the speed of sound, but begins to slow down.The size of the exhaustchambers I6 and 20 should be such, therefore,that this 50% air-pressure should not be built up therein until afterthe above-mentioned important current-zero. To provide a reasonablefactor of safety, we prefer` to have this 50% pressure occur withinabout 21/2 cycles after the opening of the blast-valve 5.

However, it is important that these exhaustchambers I6 and 20 should bepresent, and that they should develop an important back-pressure aftersaid period of 21/2 cycles or the like, and it is important that theseexhaust-chambers should be able to hold their back-pressures for a fewhalf-cycles, or until a serially connected isolating-switch 26 can beopened, as will subsequently be described. During this time, when asubstantial back-pressure is being held in the exhaust-chambers I6 and20, the blast-valve 5 must be kept open, as will readily be understood.

The air which accumulates in the two exhaustchambers I6 and 20 iscooled, in these chambers, and is slowly dissipated to the atmosphere,through suitable exhaust-openings 24, which are provided in each of theexhaust-chambers I5 and 2D, and which may be provided with any desirablemuiiling or sound-deadening or flameextinguishing means (not shown), asis well understood in the compressed-air circuit-breaker art.

Since the movable contact-members IIM and 12M are opened by theair-pressure which is exerted by a large body of fast-moving air, in ablast which moves at a velocity approximating the velocity of sound, itis impractical to sustain such a large movement or blast of air for anyconsiderable length of time. It is necessary, therefore, to close theblast-valve 5 very quickly after it is opened, so as to conserve thehighpressure air or gas which is stored in the tank or reservoir I.Consequently, after a circuit-interrupting operation by theisolating-switch 26, the blast-valve 5 is reclosed, and therefore thetwo ymovable contact-members IIM and IZM close again into contact withtheir respective stationary contact-members IIS and I2S, so that thesecontact-members thereafter remain closed throughout the time when thecircuit should remain interrupted. It is necessary, therefore, as in thecase of previously known self-opening, longitudinal-blast, orifice-typecircuit-breakers, to provide the previously mentioned isolatingswitch 26which is electrically connected in series with the interrupter-assemblyI E.

We also provide a second vertically disposed insulating column 21, whichis spaced from the blast-tube 2, and which also extends upwardly abovethe top of the tank I, so that it is supported by the tank, although itis not in pneumatic communication with the air within the tank I. Thissecond insulating column 21 is surmounted by a metal terminal-member 28,which is provided with a line-terminal 29, so as to provide the secondline-terminal of the breaker-assembly, the first line-terminal being theterminal I5 at the top of the interrupter-assembly I0. Theisolating-switch 26 is movable so as to close or open an electricalcircuit between this metal terminal-member 28 at the top of the secondinaeeaoce sulating column 21', and the bottom I4 or I6 of theinterrupter-a'ssembly IB which is mounted at the top of the insulatingblast-tube 2. In the illustrated construction, the isolating switch 26is pivotally connected to the lower exhaustchamber I6, as indicated at3D, and its free end is movable into and out of contact with suitablecontact-fingers 3|l carried by the metal terminal-member 28.

It is also a feature of the type of breaker to which our invention isapplicable, that an operating-mechanism is provided, as diagrammaticallyindicated at 33, in a location which is on, or close to, the tank I, andwhich is at substantially the same electrical potential as the tank,which would normally be grounded. Thus, this operating-mechanism 33 isphysically and electrically at the ground-level, which is ofconsiderable advantage from the standpoint of the amount and size of theequipment which must be insulatedly supported, up in the air, as by thetwo insulating supporting-columns 2 and 21. The operating-mechanism 33is operatively joined to the switch through an insulatingswitchoperating rod 34 for opening and closing the isolating-switch 26.

The operating-mechanism 33 may be controlled in any desired manner, sothat it will open the isolating-switch 26, and lock it open, after thecompletion of the arc-interruption during the opening-operation of theinterrupter-assembly I ll, and before the two movable contact-membersIIMI and I2M are spring-closed again, after a reclosure of theVblast-valve 5. In the particular design illustrated, theoperating-force, and the timing, for the operating-mechanism 33 are bothprovided by a small tube or pipe 35, which is in communication with thelower end of the insulating blast-tube 2, or the upper end of theinternal tube-means 3 in the tank I. When the blastvalve 5 first opens,the air or blast is' moving upwardly very rapidly in the blast-tube 2,sothat its static air-pressure is relatively small. This blast travelsupwardly, at a velocity approximating the velocity of sound, until itsupward movement is halted, by the top of the upper annular space 2Is, orotherwise, and then pressure begins to beA built up in this blast-'airspace, serving rst to open the two movable contactmembers IIM and IZM,after which said airpressure builds back downwardly, until the level ofthe top of the tank I is reached, at which time a suicient air-pressureis applied, through the tube 35, to begin to initiate the operation ofthe operating-mechanism 33. The inertia of the operating-mechanism 33,the insulating connecting rod 3d, and the isolating switch 26 is suchthat the isolating-switch 26 breaks its contact with the contact-fingers3l after the arcs have been interrupted by the longitudinally owinggas-blast in the two interrupter-gap devices ll and I2.

The specific construction of our` novel doublegap single-columninterrupter-assembly i6. is shown in Fig. 3, which represents apreferred form of embodiment, for illustrative purposes. The outercylinder I'io of the moving-contact assembly or housing I'I, which wasshown in Fig. l, is shown, `in Fig. 3, as a stationary opensided,open-endedboX-lke housing-member having integrally cast, ring-shaped,top and bottom members IlT and IB, which. provide the abutment-membersfor the upper and lower insulating-tubes 2l and I8, respectively.Twoopposite sides, or quadrants, of the cylindricall part I'Io of thishousing I'l are open, as shown in Fig. 3, the right-hand open side beingclosed by a cover I'IC, while the left-hand open side is closed by aflange 36 of a removable contact-supporting casting 3l which has acylindrical part 38 which is substantially coaxial with respect to theinsulating tubes I8 and 2l of the interrupter-assembly. This cylinderpart 38 corresponds to the outer surface of the inner cylinder I'Iz' inFig. 1. Fixedly but removably secured, in coaxial spaced relation withinthe cylindrical part 38 of the removable contact-supporting casting 3l,is a copper-alloy contact-carrying sleeve or cylinder 39, whichcorresponds to the inner surface of the inner cylinder I'lz in Fig. 1.Thus, the space outside of the cylindrical part 3B of the removablecasting 3l, is the annular air-blast space or enclosed interruptingchamber I'Is, as described in connection with Fig. 1, while the spaceinside of the contact-carrying sleeve 39 is occupied `by the upper andlower movable arcingcontact members ZM and lIlVi, and theirbiasing-springs IEB and HB, respectively. The copper-alloycontact-carrying sleeve 39 thus carries the current between the upperand lower moving arcing-'contacts lZM and HM. The contact-carryingsleeve 39 is smaller, in diameter, than the cylindrical part 38 of theremovable casting 33', so that there is a space ed therebetween, Thecontact-carrying sleeve 39 is held xedly in position, by means of a sortof anged and grooved bayonet-joint l, which is held, in assembledpcsition, by a suitable set-screw 2. Disposed within the space ilbetweenV the two cylindrical parts 33' and 33 of the removablemoving-contact assembly, we show upper and lower annular finger-cases 0rcontact-holders @3U and SL, respectively, which house upper and lowermain moving contacts llU and ML, respectively, which consist of clustersof coppe alloy segments which are held in said contactholders so as toform self-contained units. These contact-holders @3U and @EL are pressedoutwardly or away from each other, by means of springs @5U and liL,respectively, which normally cause the tips of the main contact-lingers4U and ML to be pressed into engagement with the ends of the respectivestationary contactmembers IES and IIS.

Each of the main contact-fingers @4U and ML is provided with two.springs, namely a radially operating spring i6 and a longitudinallyoperating spring d?. The radially operating spring 46 presses a side ofthe front end of the nger into good contact-making, sliding, engagementagainst the outer cylindrical surface of the movabile arcing-ccntactmember E2M or IIM, as the case may be. At the same time, said radialspring 53 also presses a side of the rear end of the contact-fingeragainst the outer surface of the contact-carrying sleeve 39. Thelongitudinally operating spring il? is mounted in the rear end of eachof the contact-nngers MU and ML, so as to individually press each fingerlongitudinally or axially toward the end of the corresponding staticnarycontact-member IS or I IS, as the case may be, so that each finger makesan individual spring-pressed contact-engagement with the associated.stationary contact-member, regardless of any irregularity or lack ofparallelism in either the contact-surface of the stationarycontact-niember` IS or EES, or the finger-case MU cr ZiSL.

The top or upper linger-case or, contact holder 43D has an outwardlyextending ange 59=which extends partway into the lower part or mouth ofthe upper insulating tube 2l, or into the opening in the top plate i 'ITof the moving-contact housing I 'I, so as to provide a restrictedannular space 5I, when the upper contacts are in their closed position,as shown in Fig. 3. Thus, when the blast-valve 5 (Fig. l) opens,compressed air rapidly fills the annular space A around the bottomcontacts 4.4L, in Fig. El, and also the Ispace Il under the flange 5G ofthe top contact-holder 43U. Air-flow to the space C surrounding theupper contacts 44U is restricted by this flange 5U, so that theair-pressure in this upper space C builds up more slowly than theair-pressure in the intermediate space B. As a result, the topcontact-holder 43U is initially forced upwardly, by the inrushing air,so that the upper contacts 44U remain tightly closed.

When the upward inrush of air, resulting from the opening of theblast-valve 5 in Fig. l, is halted by the flange 5U, the air-pressurebegins to build up, starting with the intermediate space B under thisflange, and backing on downwardly to the space A which surrounds thelower contacts 44L. This air-pressure in the space A quickly reaches avalue suflicient to force the lower nger-case or contact-holder 43Lupwardly against the force of its spring 45L. When the lowercontactholder 43L has moved but a short distance, it makes ahook-connection with its cluster of contact-fingers 44L, as shown at 52,and begins to raise these main contact-ngers 44h away from thestationary contact-member IIS, leaving the current to be carriedmomentarily by the moving arcing-contact member IIM, which is still incontact with the stationary contact-member I IS. As the maincontact-fingers 43L continue to move upwardly, however, under theinfluence of the air-pressure in the space A, they soon make ahook-connection, at 53, with the movable arcingcontact member IIM, thusbeginning to move this movable arcing-contact member IIM upwardly awayfrom contact with the tip of the associated contact-member I IS.

This draws an arc, which bridges the gap separating the tip of thestationary contactmember IIS and the upwardly moving lower movablearcing-ccntact IIM. The air-blast immediately rushes radially inwardlyacross this arcing gap, under the influence of the air-pressure in thespace A, and this blast of air then moves downwardly through the orice22 in the lower stationary contact-member IIS, and escapeslongitudinally downwardly through the hollow stationary contact-member IIS, to finally exhaust itself, first into the lower exhaust-chamber I5,and thence, through the exhaust-openings 24, int-o the surroundingatmosphere, as has been explained in connection with Fig. l.

In accordance with our invention, each of the stationary contact-membersIIS and I2S is provided with a concentrically disposed arc-terminal 54which is centrally held, by a suitable spiderconstruction 54', inside ofthe hollow stationary contact-member IIS or I2S, as the case may be, soas to provide a suitable, fairly uniform, airblast space for the passageof the air-blast between the arcing tip of the arc-terminal 54 and theoriced tip of the hollow stationary contactmember, and also between thesides of the arcterminal 54 and the hollow inner sides of the stationarycontact-member. The blast of air, rushing radially inwardly across thetip of the lower stationary contact-member IIS, and then longitudinallydownwardly through the orifice 22 in this member, carries the arcdownwardly and causes it to become aixed to the top of the arcterminal54, as shown in Fig. 3.

This arc-terminal 54 is provided with a central, longitudinallyextending hole 55, the top end of which is preferably enlarged orrounded, so as to cause the arc 56 to play for a short distance withinthis hole 55, thus causing the end of the are to remain centrally xedover the hole 55, instead of playing over to one side of the arcterminal54, and thus causing excessive burning and asymmetrical air-now, whichwould interfere with the proper arc-extinguishing functions. Thelongitudinal hole 55 through the arc-terminal 54 permits a small amountof air to flow longitudinally through this hole, enough to hold the arccentered on the hole, thus permitting the longitudinally ilowingair-blast to flow equally on all sides of the lower end of the arc 56,and thus exercising a maximum amount of cooling, and deionizing, andarc-extinguishing influence on the arc..

The design 0f the restricted annular space 5I which surrounds the uppercontact-holder 43U is such that the air which escapes upwardly throughthis restricted space, from the space B to the space C, requires about0.8 cycle before it builds up sufficient air-pressure, in the space C,to overcome the combined upward thrusts of the air-pressure in the spaceB and the spring 45U of the upper contact-holder 43U. Consequently, thisupper contact-holder begins to move downwardly, in a contact-openingdirection, approximately 0.8 cycle after the lower contact-holder 43Lbegan to move upwardly, in its contact-opening movement, or say between1A.; cycle and l cycle thereafter. Thereafter the order of movement ofthe parts, in the opening of the upper movable arcing-contact I2M, isessentially the same, in principle, as has been described for the lowermovable arcing-contact IIM, and the description need not be repeated.The upper stationary contact-member I2S is also provided with anarc-terminal 54 which is essentially similar to the arc-terminal 54which has already been described in connection with the lower stationarycontact-member IIS.

It should be noted that the throttling opening, or restricted annularspace 5|, between the ange 55 of the upper contact-holder 43U, and themouth of the upper insulating tube 2I, is enlarged as soon as there ismovement of the upper contact-holder 43U, thus removing all restrictionsto the free flow of air. This construcl tion has the important advantagethat the opening of the second set of contacts, that is, the uppermovable contacts, is denite, very fast, and independent of the length ofthe time-delay.

rhe reason for the provision of a construction which causes a time-delayin the opening of one of the two serially connected gaps of ourbreakerassembly, is because it was found impossible to satisfactorilyinterrupt an arcing-current of more than 15,000 to 20,000 amperes at44,000 volts, if both of the gaps were opened simultaneously. It is animportant feature of our invention, that the two gaps are openedsequentially, and that the first-opening gap shall be shunted by asuitable shunting-impedance Z, which is diagrammatically indicated inFig. 3. This shunting-impedance Z makes it possible for the lower gap tointerrupt arcing-currents as high as 37,609 amperes at 44,090 volts,even when the current is supplied by a line (not shown) havingconsiderable charging-current, or having considerabletransformer-magnetizing current there"- -in. The eiect 'of the shuntingimpedance is to delay the rate of recovery-voltage across theimpedance-shunted, iirst-opening gap, after a current-zero, so that, ingeneral, the arc will not restrike, in this impedance-shunted gap, inthe halicycle following the vfirst current-zero after fullgap-separation has been attained. As a result of this construction, theiirst-opening gap II will have substantially interrupted its arc beforethe second-opening gap i2 will be called. yupon to begin to extinguishits arc.

Thus, when the arc is extinguished in the ilrst- 4opening gap II, withinfrom 0.5 to 0.8 cycle after full contact-separation has been attained,the fault-current is caused to flow through the shunting-impedance Z,thus reducing the value of the fault-current to a relatively small valuewhich can easily be handled by the second-opening gap I2, even withoutany shunting-impedance around d the second-opening gap. Because thecurrent to be interrupted in this second-opening gap I2 is always of alow order, it is possible to increase the length of the gap-opening ofsecondopening gap, without deleteriously aecting itscurrent-interrupting ability. This is of great i i-- portance, wheninterrupting either line-charging currents, or magnetizing currents,when the value of the recovery-voltage may reach very high peaks, sothat the air-gap dielectric-strength must be increased to a maximum, inorder to prevent restriki-ng of the arc in this second-opening gap I2,after a current-Zero.

In our preferred design, as shown, our lower gaps contacts IIM, separateapproximately inch, while kour upper gaps i2, or our upper movablearcing contacts I2M, separate approximately 1% inch. The correspondingorice-openings, for the orifice 22 in the stationary contact-members IISand IZS, are approximately 1% inch diameter for the oriiice 22 in thelower stationary contactmember HS, and approximately l1/ inch diameterfor the orice 22 in the upper stationary contact-member I2S.

Since the air-passage to the upper space C is initially substantiallyshut oi, by the restricted annular1 space 5I the total initial air-flowis concentrated on the interruption of the high-current arc which playson the bottom contacts. By the time the top contacts open, the lowerexhaustchamber H5 (Fig. 1) is partly lled, so that the Velocity ofair-now in the lower gap begins to decrease, thus making available anincreasingly large amount of air-now which is directed toward the uppercontacts and the interruption of the current which flows through theshunting impedance Z. This has the combined eiect of improving theinterrupting capacity of the breaker, and conserving the compressed air.

In order to prevent the accumulation of internal air-pressures, insideof the moving-contact assembly, which might interfere with the uniformoperation of the device, the internal space within the contact-carryingsleeve 39, may be vented by a radial vent 5S through the wall or" thiscontactsleeve, as indicated; while the space 4? between thecontact-sleeve 33 and the cylindrical part 33 may be vented to the outeratmosphere, through a suitable vent 65 in the removablecontact-supporting casting 3l, as indicated in Fig. 3.

The removable moving-contact assembly can be removed by unfastening theflange 3e of the removable contact-supporting casting 3'.' from the sideof the box-like stationary contact-sup- II, or high-current-interruptingarcingport I1, after a suitable tong-shaped tool 62 has been inserted inan opening which is provided in the flange 36, and used to force themoving contacts to their open-circuit positions. This tool 62 may nt in,on either side, or on both sides, or" the cylindrical part 33 of theremovable casting 3l', so as to engage hooks t3 which are provided onthe upper and lower contact-holders BU and QSL. rhe necessary pressurefor the compression of the several springs within the movingcontactassembly is provided by a screw Sil, in the handle of the tool52, which makes it possible to contra-ct the movable parts into theirfull-open position.

It will be noted that the tips of the two stationary contact-members HSand iZS are spaced back, a slight distance, behind the ends of thecorresponding insulating tubes I8 and ZI, and that the main and arcingmoving-contacts normally project out beyond the respective ends of theirguiding-sleeves, so as to make contact with these back-set tips of therespective stationary contacts. Consquently, when the moving contactsare compressed to their open positions, the entire moving-contactassembly, which is carried by the removable contact-supporting casting3l, can be moved laterally out of the box-like housing l?.

As this movable contact-assembly is somewhat heavy for one man tohandle, the cover i'iC has been provided, for the other side of thebox-like housing il, not only for inspection-purposes, but also so that,when this cover HC is removed, a rod or handle E55 may be attached tothat side of the removable casting 37, so that two men may easily removethe removable assembly.

The destructive swaging of the abutment-parts, which limit the movementof the fast-moving parts of our breaker, has heretofore been quite aproblem, resulting in excessive deformation of the parts, as Well asundesirable noise. These diiliculties have been avoided by the use ofsuitable damping-means or shock-absorbers, interposed between tlieabutments which limit the opening-movements of the various parts, andthe most suitable damping-means, for this purpose, has been found to bea large number of extremely thin metal damping-washers Si, a suitablestack of which is interposed between each of the abutment-surfaces whichlimit the opening-movements of the contact-holders 3U and QSL, and alsothe opening movements of the two movable arcing-contacts HM and IZM.

The movable arcing-contacts HM and IZM are provided with centrallydisposed arcing-tips 6d, made of a suitable arc-terminal metal, such asa mechanical mixture of tungsten and silver or a mechanical mixture oftungsten and copper, as is known in the art. These metal inserts carrythe arc-terminal during most of the arcing time, that is, during most ofthe time before the current-zero at which the arc is interrupted, asindicated in the lower gap in Fig. 3.

The operation of the device has been indicated as the description hasproceeded. It will be observed that the main contact-iingers U and 4Lare disposed in shielding-relationship with respect to the movablearcing-members IEM and I IM, so as to shield the latter from receivingthe effects of the air-pressure until the main contacts have separated.This prevents an arc from being drawn on the tips of the main contacts,which would roughen them and destroy their ability to carry largecurrents without overheating, in the closed position of the breaker. Ii,

however, for any reason, an arc should form on the main contacts, itwill be noted that these contacts are in the air-stream, which willimmediately blow such an arc off of the main contacts, and transfer itonto the movable arcing-contacts, where it belongs.

In the closing movement of the breaker, the same construction whichcauses the main contacts to open first, causes the arcing-contacts toclose rst, so that the main contacts are protected against the arcswhich might be formed as the zero-gap point approaches, near the end ofthe closing-movement, particularly when our invention is applied to aquick-reclosing breaker.

It is believed that the other features of our invention have beensufficiently well described as the description has proceeded.

Various details of the breaker-assembly, which is herein generically orbroadly described and claimed, are described and claimed in more detailin other copending applications. Thus, the general combination,including the blast-valve 5, is claimed in the previously mentionedBaker- Wilcox application. Certain improvements and novel features ofthe pneumatic operating assembly, including the operating mechanism 33,insulating switch-operating rod 34, isolatingswitch 2B, pneumaticcontrolling-means including the tube 35, and an interlocking-means (nothere shown) for automatically reclosing the blastvalve 5 when theisolating-switch 25 has completed enough of its opening-movement, areshown and claimed in a copending application, Serial No. 73,516, ledJanuary 29, 1949, by Baker and Wilcox. And finally, certain structuraldetails oi the interrupter-assembly i il, for mechanically holding theparts of this assembly together, are shown in more detail, andspecifically claimed, in a copending application, Serial No. 74,407,filed February 3, 1949, now U. S. Patent 2,602,868, is-

sued July 8, 1952, Ito Benjamin P. Baker, Erling Frisch, and Howard M.Wilcox.

While we have described and illustrated our invention in but a singleillustrative form, which is shown somewhat diagrammatically or ideally,we wish it to be understood that Vwe are not limited to the precise formwhich is illustrated, as those skilled in the art could readily makevarious changes of substitution, omission or addition, without departingfrom the essential spirit of our invention. We desire, therefore, thatthe appended claims shall be accorded the broadest constructionconsistent with their language.

We claim as our invention:

1. An interrupter-assembly for a compressedair circuit-breakercomprising: an enclosed interrupting chamber, a hollow elongatedstationary contact-member disposed within said chamber having an oricein its front end; a substantially closed exhaust-chamber at the rear endof said stationary contact-member in aircommunication with its hollowinterior; a moving-contact assembly comprising a spring-closed,longitudinally movable contact-member normally abutting against thefront end of said stationary contact-member and in such positionsubstantially covering said orice; and means for, at times, supplying ablast of compressed air to the enclosed interrupting chamber surroundingthe abutting ends of the two contactmembers; said exhaust-chamber havingmeans for permitting a slow air-exhaustion therefrom and therebypreventing free venting of the enclosed interrupting chamber toatmosphere during the time of contact separation and having-a capacitysuch as to build up, in said exhaust-chamber, a pressure equal to about50 percent of the pressure in the enclosed interrupting chambersurrounding the normally abutting ends of the two contact-members in atime not much longer than the time necessary for the moving member tomove back to full contact-gap-separation under the iniiuence of theair-pressure of the applied air-blast and for the longitudinally flowingair-blast in the orifice to extinguish the resulting arc.

2. A multigap breaker comprising at least two interrupter-assemblies,each interrupter-assembly comprising: an enclosed interrupting chamber,a hollow elongated stationary contactmember disposed within said chamberhaving an orifice in its front end; a substantially closedexhaust-chamber at the rear end of said stationary contact-member inair-communication with its hollow interior; a moving-contact assemblycomprising a spring-closed, longitudinally movable contact-membernormally abutting against the front end of said stationarycontact-member and in such position substantially covering said oriiice;and means for, at times, supplying a blast of compressed air to theenclosed interrupting chamber surrounding the abutting ends of the twocontact-members; said exhaust-chamber having means for permitting a slowair-exhaustion therefrom and thereby preventing free venting of theenclosed interrupting chamber to atmosphere during the time of contactseparation and having a capacity such as to build up, in saidexhaust-chamber, a pressure equal to about 50 percent of the pressure inthe enclosed interrupting chamber surrounding the normally abutting endsof the two contact-members in a time not much longer than the timenecessary for the moving member to move back to fullcontact-gap-separation under the influence of the air-pressure of theapplied air-blast and for the longitudinally flowing air-blast in theorifice to extinguish the resulting arc, the blast-supplying means beingsuch as to apply an effective contact-separating air-pressure to one ofthe interrupter assemblies early enough before the otherinterrupterassembly so that the iirst-opening gap will havesubstantially interrupted its arc before the second-opening gap will becalled upon to begin to extinguish its arc, said two interrupterassemblies being electrically connected in series circuit relation, incombination with a shunting-impedance electrically connected in shuntaround the first-opening gap.

3. A multigap breaker comprising an enclosed interrupting chamber, atleast two interrupterasse iblies disposed within said chamber; eachcomprising a hollow elongated stationary contact-member having an oricein its front end, a moving-contact assembly comprising acontact-carrying sleeve, a spring-closed, longitudinally movablecontact-member carried by said sleeve, said stationary contact-memberand said sleeve being in substantial alignment, the movablecontact-member normally abutting against the frontend of said stationarycontact-member and in such position substantially covering said orifice,said two interrupter assemblies being electrically connected in seriescircuit relation; in combination with means for, at times, supplying ablast of compressed air to said enclosed interrupting chamber, theblast-supplying means being such as to apply an eiectivecontactseparating air-pressure to one of the interrupter assembliesearly enough before the other interrupter-assembly so that thefirst-opening gap will have substantially interrupted its arc before thesecond-opening gap will be called upon to begin to extinguish its arc, asubstantially enclosed exhaust chamber in pneumatic communication withat least one of the hollow stationary contact members andV therebypreventing free venting of the gas blast to atmosphere during the timethe contacts are separated, and a shunting-impedance electricallyconnected in shunt around the first-opening gap.

4. A multigap breaker comprising at least two interrupter-assemblies,each interrupter-assembly comprising: an enclosed interrupter chamber, ahollow elongated stationary contact-member disposed within said chamberhaving an orifice in its front end; a substantially closedexhaust-chamber at the rear end of said stationary contact-member inair-communication with its hollow interior; a moving-contact assemblycomprising a spring-closed, longitudinally movable contact-membernormally abutting against the front end of said stationarycontact-member and in such position substantially covering said orice;and means for, at times, supplying a blast of compressed air `to theenclosed interrupting chamber surrounding the abutting ends of the twocontact-members; said exhaust-chamber having means for permitting a slowair-exhaustion therefrom and thereby preventing free venting of theenclosed interrupting chamber to atmosphere during the time of Contactseparation and having a capacity such as to build up, in saidexhaust-chamber, a pressure equal to about 50 percent of the pressure inthe enclosed interrupting chamber surrounding the normally abutting endsof the two contact-members in a time not much longer than the timenecessary for the moving member to move back to fullcontact-gap-separation under the iniiuence of the air-pressure of theapplied air-blast and for the longitudinally flowing air-blast in theorifice to extinguish the resulting arc, the blast-supplying means beingsuch as to apply an eiTective contactseparating air-pressure to one ofthe interrupter assemblies early enough before the otherinterrupter-assembly so that the first-opening gap will havesubstantially interrupted its arc before the second-opening gap will becalled upon to begin to extinguish its arc, said two interrupterassemblies being electrically connected in series circuit relation, incombination with a shuntingimpedance electrically connected in shuntaround the nist-opening gap, the second-opening moving contact-memberhaving a materially longer gap-separation than the rst.

5. A multigap breaker comprising an enclosed interrupting chamber, atleast two interrupterassemblies disposed within said chamber, eachcomprising a hollow elongated stationary contact-member having an oricein its front end, a moving-contact assembly comprising a contactcarryingsleeve, a spring-closed, longitudinally movable contact-member carriedby said sleeve, said stationary contact-member and said sleeve being insubstantial alignment, the movable contact-member normally abuttingagainst the front end of said stationary contact member and in suchposition substantially covering said orice, said two interrupterassemblies being electrically connected in series circuit relation; incombination with means for, at times, supplying a blast of compressedair to said enclosed interrupting chamber, the blast-supplying meansbeing such as to apply an effective contactseparating air-pressure toone of the interrupter assemblies early enough before the otherinterrupter-assembly so that the first-opening gap will havesubstantially interrupted its arc before the second-opening gap will becalled upon to begin to extinguish its arc, a substantially enclosedexhaust chamber in pneumatic communication with at least one of thehollow stationary contact members and thereby preventing free venting ofthe gas blast to atmosphere during the time the contacts are separated,and a shunting-impedance electrically connected in shunt around thefirst-opening gap, characterized by the second-opening movingcontact-member having a materially longer gap-separation than the first.

6. A single-column, double-gap, interrupterassembly for a compressed-aircircuit-breaker, comprising, at each end of the assembly, an inwardlyextending hollow elongated stationary contact-member having itsYarcing-end toward the center of the assembly and having an orice insaid arcing-end, an insulating tube `surrounding each stationarycontact-member in spaced relation thereto to provide an air-spacetherearound, an open-sided open-ended moving-contact housing disposed inabutting engagement with the inner ends of the respective insulatingtubes, a removable contact-supporting member having a'lange which closesthe open side of said housing and having a contact-carrying sleeve whichis disposed substantially coaxially with respect to said insulatingtubes, a longitudinally movable contact-member carried by each end ofsaid contact-carrying sleeve, a biasing-spring tending to press eachmovable contact-member out of said sleeve and normally holding eachmovable contact-member in contact with the arcing-end of the associatedstationary contact-member, and air-blast means for, at times, supplyinga contact-opening and arc-extinguishing blast of compressed air to thespace between one of said insulating tubes and its associated stationarycontact-member.

7. An interrupter-assembly for a compressedair circuit-breaker,comprising a hollow elongated stationary contact-member having anorifice in its front end, a moving-contact assembly comprising, ineiect, two spaced concentric cylinders, a movable arcing-contact memberlongitudinally slidable within the inner cylinder and extending beyondthe end thereof, a biasing-spring tending to press said movablearcing-contact member out of said inner cylinder and normally holdingsaid movable arcingcontact member in orifice-closing contact with thefront end of said stationary contact-member, a cluster of maincontact-lingers surrounding said movable arcing-contact member, eachcontact-finger having lateral abutting-contact against the outer surfaceof said inner cylinder, a contact-holder surrounding said cluster ofmain contact-fingers, said contact-holder being longitudinally slidablewithin the outer cylinder and extending beyond the end oi said outercylinder, spring-means for yieldably pressing each contact-lingerlaterally inwardly, a biasingspring tending to press the contact-holderout of said outer cylinder, enclosure-means for providing agap-surrounding air-space surrounding the abutting ends of thecontact-fingers: and the stationary contact-member, and means 17 for, attimes, supplying a blast of compressed air to said gap-surroundingspace.

8. An interrupter-assembly for a compressedair circuit-breaker,comprising a hollow elongated stationary contact-member having an oricein its front end, a moving-contact assembly comprising, in effect, twospaced concentric cylinders, a movable arcing-contact memberlongitudinally slidable within the inner cylinder and extending beyondthe end thereof, a biasing-spring tending to press said movablearcing-contact member out of said inner cylinder and normally holdingsaid movable arcing-contact member in orifice-closing contact with thefront end of said stationary contact-member, a cluster of maincontact-fingers surrounding said movable arcing-contact member, eachcontactfinger having lateral abutting-contact against the outer surfaceof said inner cylinder, a contact-holder surroundingl said cluster ofmain contact-lingers, said contact-holder being longitudinally slidable.within the outer cylinder and extending beyond the end of said outercylinder, spring-means for yieldably pressing each contact-fingerlaterally inwardly, a biasingspring tending to press the contact-holderout of said outer cylinder, enclosure-means for providing agap-surrounding air-space surrounding the abutting ends of thecontact-fingers and the stationary contact-member, and means for, attimes, supplying a blast of compressed air to said gap-surroundingspace, characterized by said main contact-fingers, when they have movedslightly away from the stationary contact-member, under the inuence ofthe airblast pressure, having means for making a contact for carryingalong the movable arcingcontact member.

9. An interrupter-assembly for a compressedair circuit-breaker,comprising a hollow elongated stationary contact-member having anorifice in its front end, a moving-contact as.- sembly comprising, ineffect, two spaced concentric cylinders, a movable arcing-contact memberlongitudinally slidable within the inner cylinder and extending beyondthe end thereof, a biasing-spring tending to press said movablearcing-contact member out of said inner cylinder and normally holdingrsaid movable arcing-contact member in orifice-closing contact with thefront end of said stationary contact-member, a cluster of maincontact-fingers, each having lateral abutting-contact against the outersurface of said inner cylinder and another lateral abutting-contact withan outer surface of the projecting end of said movable arcing-contactmember, beyond the end of said inner cylinder, a. contact-holdersurrounding said cluster of main contact-fingers, said contact-holderbeing longitudinally slidable within the outer cylinder and extendingbeyond the end of said outer cylinder, spring-means for pressinglaterally inwardly against the contact-fingers, a separatelongitudinally acting spring-means interposed between the rear end ofeach contact-finger and the contact-holder, another biasing-springtending to press the contact-holder out of said outer cylinder andnormally holding the front ends of said contact-fingers in contact withthe front end of said stationary contact-member, enclosure-means forproviding a gap-surrounding air-space surrounding the abutting ends ofthe contact-fingers and the stationary contactmember, and means for, attimes, supplying a ISU 18 blast of compressed air to saidgap-surrounding space.

10. An interrupter-assembly for a compressedair circuit-breaker,comprising a hollow elongated stationary contact-member having anorifice in its front end, a moving-contact assembly comprising, ineffect, two spaced concentric cylinders, a movable arcing-contact memberlongitudinally slidable within the inner cylinder and extending beyondthe end thereof, a biasing-spring tending to press said movablearcing-contact member out of said inner cylinder and normally holdingsaid movable arcingcontact member in orice-closing contact with thefront end of said stationary contact-member, a cluster of maincontact-iingers, each having lateral abutting-contact against the outersurface of said inner cylinder and another lateral abutting-contact withan outer surface of the projecting end of said movable arcing-contactmember, beyond the end of said inner cylinder, a contact-holdersurrounding said cluster of main contact-fingers, said contact-holderbeing longitudinally slidable within the outer cylinder and extendingbeyond the end of said outer cylinder, spring-means for pressinglaterally inwardly against the contact-ngers, a separate longitudinallyacting spring-means interposed between the rear end of eachcontact-iinger and the contact-holder, another biasing-spring tending topress the contact-holder out of said outer cylinder and normally holdingthe front ends of said contact-fingers in contact with the front end ofsaid stationary contact-member, enclosure-means for providingl agap-surrounding air-space surrounding the abutting ends of thecontact-fingers and the stationary contactmember, and means for, attimes, supplying a blast of compressed air to said gap-surroundingspace, characterized by said main contactfingers, when they have movedslightly away from the stationary contact-member, under the influence ofthe air-blast pressure, having means for making a Contact for carryingalong the movable arcing-contact member.

11. A single-column, double-gap, interrupterassembly for acompressed-air circuit-breaker, comprising, at each end of the assembly,an inwardly extending hollow elongated stationary contact-member havingits arcing-end toward the center of the assembly and having an orificein said arcing-end, an insulating tube surrounding each stationarycontact-member in spaced relation thereto to provide an air-spacetherearound, an open-sided open-ended moving-contact housing disposed inabutting engagement with the inner ends of the respective insulatingtubes, a removable contact-supporting member having a flange whichcloses the open side of said housing, said removable contact-supportingmember also having, in eiect, two spaced concentric cylinders which aredisposed substantially coaxially with respect to said insulating tubes,a longitudinally movable arcing-contact member carried by each end ofthe inner cylinder of said removable contact-supporting member, eachmovable arcing-contact member being longitudinally slidable within theinner cylinder and extending beyond the end thereof, a biasingspringtending to press each movable arcingcontact member out of said innercylinder and normally holding said movable arcing-contact member inorifice-closing contact with the front end of the correspondingstationary contactmember, a cluster of main contact-fingers as- ,movablearcing-contact member,

whereby the two contact-holders. may, at times, e

19 sociated with each movable arcing-contact member, each contact-fingerhaving a lateral abutting-contact against the outer surface of saidinner cylinder, a separate contact-holder surrounding each of saidclusters of main contactngers, each contact-holder being longitudinallyslidable within the outer cylinder and extending beyond the end of saidouter cylinder, springmeans for pressing each contact-iinger laterallyinwardly, a biasing-spring tending each contact-holder out of said outercylinder, air-blast means for, at times, supplying a contact-opening andarc-extinguishing blast of compressed air to the space between one ofsaid insulating tubes and its associated stationary contact-member, eachof said contact-holders, when it has moved slightly axially inwardlyagainst the pressure of its biasing-spring, having means for makingcontact for carrying along its cluster of contact-iingers, each clusterof e.

contact-fingers, when it has moved slightly away from the associatedstationary contact-finger, having means for carrying along theassociated and means inwardly extending hollow elongated stationarycontact-member having its arcing-end toward the center of the assemblyand having an orice in said arcing-end, an insulating tube surroundingeach stationary contact-member in spaced relation thereto to provide anair-space therearound, a moving-contact assembly disposed in abuttingengagement with the inner ends of the respective insulating tubes, saidmoving-contact assembly including a contact-carrying sleeve which isdisposed substantially coaXially with respect to said insulating tubes,a longitudinally movable contact-member carried by each end of saidcontact-carrying sleeve, a biasing-spring tending to press each movablecontact-member out of said sleeve and normally holding each movablecontact-member in contact with the arcing-end of the associatedstationary contactmember, and air-blast means for, at times, supplying acontact-opening and arc-extinguishing blast of compressed air to thespace between one of said insulating tubes and its associated stationarycontact-member, the entrance to the inner end of the insulating tubeopposite to the tube through which the air-blast is supplied beingnormally, in the closed-contact position, closed to a restricted spaceby a portion of the movable contact-member at that end of the assembly,whereby said restricted space causes that movable contact-member toreceive an adequate contact-separating air-pressure only after the othercontact-member has been opened, said second-opening contact-member, whenit iirst begins to open, moving out of said entrance to its associatedinsulating tube, so that said second-opening movable contact-memberthereafter receives a substantially unrestricted airblast to cause arapid and positive contactopening movement and an adequatearc-extinguishing blast.

13. A single-column, double-gap, interrupterto press i@ assembly for acompressed-air circuit-breaker, comprising, at each end of the assembly,an inwardly extending hollow elongated stationary contact-member havingits arcing-end toward the center of the assembly and having an orificein said arcing-end, an insulating tube surrounding each stationarycontact-member in spaced relation thereto to provide an air-spacetherearound, an open-sided open-ended moving-contact housing disposed inabutting engagement with the inner ends of the respective insulatingtubes, a removable contact-supporting member having a flange whichcloses the open side of said housing and having a contact-carrying Isleeve which is disposed substantially coaxially with respect to saidinsulating tubes, a longitudinally movable contact-member carried byeach end of said contact-carrying sleeve, a biasing-spring tending topress each movable contact-member out of said sleeve and normallyholding each movable contact-member in contact with the arcing-end ofthe associated stationary contact-member, and air-blast means for, attimes, supplying a contact-opening and arc-extinguishing blast ofcompressed air to the space between one of said insulating tubes and itsassociated stationary contact-member, characterized by the entrance tothe inner end of the insulating tube opposite to the tube through whichthe air-blast is supplied being normally, in the closed-contactposition, closed to a restricted space by a portion of the movablecontact-member at that end of the assembly, whereby said restrictedspace causes that movable contact-member to receive an adequatecontact-separating air-pressure only after the other contact-member hasbeen opened, said second-opening contact-member, when it rst begins toopen, moving out of said entrance to its associated insulating tube, sothat said second-opening movable contact-member thereafter receivesV asubstantially unrestricted air-blast to cause a rapid and positivecontact-opening movement and an adequate arc-extinguishing blast.

14. A single-column, double-gap interrupterassembly for a compressed-aircircuit-breaker, comprising, at each end of the assembly, an inwardlyextending hollow elongated stationary contact-member having itsarcing-end toward the center of the assembly and having an orifice insaid arcing-end, an insulating tube surrounding each stationarycontact-member in spaced relation thereto to provide an air-spacetherearound, an open-sided open-ended moving-contact housing disposed inabutting engagement with the inner ends of the respective insulatingtubes, a removable contact-supporting member having a flange whichcloses the open side of said housing, said removable contact-supportingmember also having a cylindrical part which vis i-lxedly united withlsaid flange, said removable contact-supporting member being furtherprovided with a separable contact-carrying sleeve having a sort ofremovably locked bayonet-joint connection for holding it in spacedcoaxial relation within said cylindrical part, said cylindrical part andsaid contact-carrying sleeve being disposed substantially coaxially withrespect to said insulating tubes, a longitudinally movablecontact-member carried by each end of said contact-carrying sleeve,spring-means for yieldably pressing each movable contact- Hmember intoits normal contact-making position,

and air-blast means for, at times, supplying a contact-opening andarc-extinguishing blast of compressed air to the space between one ofsaid insulating tubes and its associated stationary contact-member.

15, A self-opening, orifice-type, air-blast circuit-interrupterassembly, comprising springclosed, longitudinally separablearcing-contacts, at least one of which is provided with an orifice whichis closed by the other contact in the no1'- mal closed position of theassembly, said oriced contact also having a longitudinal passage for theow of an arc-extinguishing air-blast therein, and means for, at times,supplying a blast of compressed air to the space surrounding saidcontacts, whereby the air-pressure of said blast causes acontact-separation and then extinguishes the resulting arc, incombination with a cluster of main contact-fingers normally surroundingthe space around the separable arcingcontacts so as to partially shieldthe arcingcontacts from the initial effects of the blast, means forbiasing each contact-iinger laterally toward a surface of onecontact-member of the circuit-interrupter and longitudinally toward asurface of the other contact-member of the circuit-interrupter, therelations between the pneumatic pressure-surfaces and the longitudinallyacting closure-springs being such that the main contact-iingers openfirst, in response to the air-blast, and then the arcing-contactsseparate and the blast iiows into said orifice and said longitudinalpassage after rst passing the opened contact-fingers.

16. A self-opening, oriiice-type, air-blast circuit-interrupterassembly, comprising springclosed, longitudinally separablearcing-contacts, at least one of which is provided with an orifice whichis closed by the other contact in the normal closed position of theassembly, said oriiiced contact also having a longitudinal passage forthe 110W of an arc-extinguishing air-blast therein, and means for, attimes, supplying a blast of compressed air to the space surrounding saidcontacts, whereby the air-pressure of said blast causes acontact-separation and then extinguishes the resulting arc, incombination with a cluster of main contact-lingers normally surroundingthe space around the separable arcingcontact so as to partially shieldthe arcingcontacts from the initial effects of the blast, means forbiasing each contact-finger laterally toward a surface of onecontact-member of the circuit-interrupter and longitudinally toward asurface of the other contact-member of the circuit-interrupter, therelations between the pneumatic pressure-surfaces and the longitudinallyacting closure-springs being such that the main contact-fingers openrst, in response to the air-blast, and then the arcing-contacts separateand the blast flows into said orifice and said longitudinal passageafter rst passing the opened contact-lingers, in combination with acontact-holder surrounding said cluster of main contact-fingers andhaving a biasing-spring for normally biasing said holder longitudinallytoward the closed position of said contact-iingers.

BENJAMIN P. BAKER.

ERLING FRISCH.

WAYNE S. ASPEY.

JOHN B. MACNEILL.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,125,525 Thommen Aug. 2, 19382,255,198 Thommen Sept. 9, 1941 2,306,186 Rankin Dec. 22, 1942 2,306,240Wyman Dec. 22, 1942 2,407,537 Chapman Sept. 10, 1946 2,440,995 WilcoxMay 4, 1948 2,453,555 Thommen Nov. 9, 1948 2,458,240 Baskerville Jan. 4,1949 2,491,821 Lerstrup Dec. 20, 1949

